This invention relates to devices and methods for removing an occlusion from a vessel.
This surgical device is designed to remove occlusions found in the human vasculature and thereby increase blood flow to and around the occluded site.
Emboli occasionally form around the valves of the heart and then are dislodged and follow the blood flow into the distal regions of the body. They are particularly dangerous if the emboli is transmitted to the brain where it results in an embolic stroke. As will be discussed below, many such occlusions occur in the middle cerebral artery (MCA), although such is not the only site where emboli come to rest. When blood flow is inhibited or cut off completely from a portion of the brain, the brain""s oxygen supply is limited causing severe problems.
Such vaso-occlusions occur in a wide variety of sites within the body. The lodging of thrombus in various sites is complicated by the presence of atherosclerosis. This disease causes the vessels to become tortuous and narrowed. These anomalies are often considered to be the result of the growth of atherosclerotic plaque. Clots occurring in these diseased vessels are difficult to remove using known catheters.
The use of inflatable balloons to remove emboli has been practiced for many years. The xe2x80x9cFogarty catheterxe2x80x9d has been used, typically in the periphery, to remove clots from arteries found in legs and in arms. These well known devices have been described in some detail in U.S. Pat. No. 3,435,826, to Fogarty. Other balloon-type devices are described, for example, in U.S. Pat. Nos. 4,403,612; 3,367,101; 5,078,722; 5,836,957; and 6,152,909.
Another approach for removing embolisms involves the use of an abrading device carried at the distal end of a flexible drive shaft. Examples of such devices are described, for example, in U.S. Pat. No. 4,990,134 (Auth) and U.S. Pat. No. 5,314,438 (Shturman) which describe the use of abrasive material such as diamond grit (diamond particles or dust) to remove hardened, calcified atherosclerotic plaques. Emboli fragmenting devices have also been described, for example, in U.S. Pat. No. 5,423,838. Other patents describe the use of cutting blades, typically extendable from a housing assembly for removing the occlusion by fragmentation. See, for example, U.S. Pat. Nos. 4,030,503; 4,890,611; 5,411,509; 5,490,859; 6,001,112; 5,423,838; and 4,923,462. These devices typically contain a catheter shaft, a drive shaft for spinning the material movement element within the blood vessel, and a collection portion placed on the material removal element for collecting any occlusion material removed by the expandable material removal element. The drive shaft may be operated by a motor connected to the drive shaft proximate to the proximal end of the drive shaft.
Despite the advances made using these devices, removal of emboli using either balloon catheters or mechanical fragmenting devices is rife with potential problems. When attempting to remove a clot using a balloon catheter, the resistance to such removal often causes the balloon portion of the catheter to evert over the tip of the catheter. Should the user need to partially deflate the balloon during such a deflation, the distal tip of the balloon may become distended and angulate. Another difficulty with balloon catheters is the possibility of damage to the intima of arteries. Inflation pressures can create forces significant enough to share such a vessel lining or dislodge plaque lodged on such a wall. In the worst case, the balloon may rupture leaving balloon portions in the bloodstream. Movement of a balloon can displace the clot through more proximal branches into other large vessels such as the internal carotid artery (ICA) and then into other vessels. Furthermore, if the occlusion is a blood clot or soft tissue thrombus, such as those that may occur in the peripheral vasculature, for instance, the soft tissues of the thrombus may sufficiently resist the molding action of the dilating member (i.e. may be too elastic) to prevent conventional angioplasty from permanently restoring vascular blood flow. In addition, even if the occlusion is successfully molded, thereby revascularizing the vessel and restoring blood flow therethrough, there is a chance that the occlusion may recur because the occluding material is not removed from the vascular lumen, thereby necessitating repeated or alternative treatments.
Mechanical fragmenting devices can also cause serious problems during clot removal. For example, because embolisms are often asymmetrical or are similar in mechanical properties to the surrounding tissue, many of these devices can damage healthy tissue while removing the clot. Furthermore, many fragmenting devices are not suited to removing both hard and soft occlusions. Additionally, the fragments generated by mechanical fragmentation cannot always be efficiently removed and can cause problems if they are carried by the blood to remote locations.
Thus, notwithstanding the foregoing and other efforts to design a embolic removal devices, there remains a need for such a device which can efficiently remove all sorts of emboli while providing minimal risk to the surrounding vessel wall. None of the currently available devices approximates the design of the device described below.
In one aspect, the invention includes a device for removing occlusions from a vessel, comprising (a) a housing element having a distal end, a proximal end and a longitudinal axis, wherein one or more lumens are disposed along the longitudinal axis; (b) an embolism collector element (e.g., a vacuum aspirator); (c) a cutting element attached to the distal end of the drive shaft; and (c) an inflatable balloon. In certain embodiments, the device further includes one or more of the following components: a fluid channel, a casing (e.g., a cage-like structure) disposed around the cutting element; a drive shaft disposed along the longitudinal axis of the housing and/or a power source (e.g., a micro electro mechanical system (MEMS) motor). In any of these devices, the cutting element may be smooth, roughened and/or may have perforations therein. Similarly, in any of these devices the housing and/or casing that contacts the cutting element is also surface-modified (e.g., is roughened, perforated, includes braids and/or ribbons, etc.). In embodiments comprising a casing around the cutting element, the casing may extend from the distal end of the housing. In any of the devices described herein, the inflatable balloon is capable of (a) centering the cutting element; (b) at least partially arresting blood flow around the occlusion; or (c) both centering and arresting blood flow.
In another aspect, methods of removing an occlusion in a vessel are provided. The methods comprise accessing a selected site with any of the devices described herein; inflating the balloon to the desired dimensions; shearing at least a portion of the embolism with the cutting element; and removing the sheared fragments of the embolism with the collection element. In certain embodiments, the shearing comprises drawing a portion of the embolism into the housing and manipulating the cutting element to shear the embolism against the interior wall of the housing and/or against the casing, when the casing is present.
These and other embodiments of the subject invention will readily occur to those of skill in the art in light of the disclosure herein.